Nearly all the arguments, both in favor of and opposed to American intervention in Syria, appear to make sense and are based on reasonably logical analysis. Thus the pros and cons tend to cancel each other out.

But that doesn’t let President Obama off the hook. He has to decide, with the help of allies such as the British and the French, what is the strategy that most likely would produce the best results, and in this case the best results are those that involve the fewest unintended consequences.

It’s one thing to knock out Syria’s capacity to use chemical weapons, or to destroy Syrian airfields. It’s another to do so without serious collateral damage within Syria and dangerous responses from Syria’s supporters.

For example, Iran, a nation that seemed on the brink of at least modifying its long-standing enmity toward Washington, has loudly warned that if the United States attacks targets in Syria, the entire region — and in this context, that means Israel — will be subject to massive retaliation.

That’s because, in a region where one major branch of Islam is almost always at war with the other, Iran supports the brutal Syrian dictatorship of Bashar al-Assad just as much as it despises the very existence of Israel. In Lebanon, the same holds true with the Israel-hating Hezbollah. In short, the civil war in Syria doesn’t respect borders.

And Obama has made it clear his goal is not to remove Assad from power. That’s simply because, wisely, he doesn’t trust what would follow in a country where the rebels are fighting among each other and where imported jihadists, sympathetic to al-Qaida, may prevail in the war’s aftermath.

Donald Rumsfeld, who as secretary of defense advised President George W. Bush, declared that Obama has yet to provide a reasonable rationale for attacking Syria. He may actually be right, but it’s difficult to overlook the fact that Rumsfeld’s judgment comes with some pretty ugly baggage. Just ask Colin Powell, who had the embarrassing task of presenting the dubious evidence of Iraqi weapons of mass destruction to the United Nations.

But what if, in this instance, Rumsfeld is right? Until there’s absolute certainty that the Assad regime did use chemical weapons, there’s no widely accepted proof that the so-called red line has been crossed. Obama insists he has that proof, but can he convince others, especially those who remember the Bush administration’s “proof” that Saddam Hussein possessed WMDs?

But if Obama doesn’t take some action to punish Syria, it will be taken as a sign of weakness, not just by his domestic critics but especially by those who expect Americans to rush to their rescue whenever the peace is threatened. Given the realities in the Middle East, that would only give the jihadists more propaganda to convince others that Washington is weak.

An international treaty known as the Geneva Protocol has, since 1928, prohibited the first use of chemical and biological weapons. It was amended twice, in 1972 and 1993, to also ban the production, storage or transfer of such horrible weapons. The treaty forbids the use of “asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices” as well as “bacteriological methods of warfare.”

But Syria never signed the treaty.

So why, instead of Obama or the United Nations making a decision, shouldn’t Assad himself defuse the crisis? He could simply sign the treaty and abide by its rules.

That won’t happen. Assad is nothing if not stubborn. And so the debate rages on, just like the civil war itself.